An electrostatic chuck is used to attract and hold a processing object such as a semiconductor wafer, a glass substrate, etc., inside a plasma processing chamber that performs etching, CVD (Chemical Vapor Deposition), sputtering, ion implantation, ashing, etc. The electrostatic chuck applies electrical power for electrostatic attraction to a built-in electrode and attracts and holds a substrate such as a silicon wafer, etc., by an electrostatic force.
In recent years, it is desirable to downsize and increase the processing speed of an IC chip including a semiconductor element such as a transistor, etc. Accordingly, it is desirable to increase the precision of the patterning such as etching, etc., when forming the semiconductor element on the wafer. The patterning precision of the etching indicates whether or not a pattern having the designed width and/or depth can be formed by patterning the wafer. By increasing the patterning precision of the etching, etc., the semiconductor element can be downscaled; and the integration can be increased. In other words, by increasing the patterning precision, faster speeds and downsizing of the chip are possible.
It is known that the patterning precision of etching or the like is dependent on the temperature of the wafer when patterning.
Therefore it is desirable to stably control the temperature of the wafer when patterning in a substrate processing apparatus including an electrostatic chuck. For example, the ability to cause the temperature distribution in the wafer surface to be uniform (temperature uniformity) is desirable. Also, the ability to deliberately set a temperature difference in the wafer surface (temperature controllability) is desirable. As a method for controlling the temperature of the wafer, a method is known in which an electrostatic chuck including a heater (a heating element) and/or a cooling plate is used (JP-A 2010-40644 (Kokai)).
A pattern that has a planar configuration is provided in a heater built into an electrostatic chuck. Thereby, for example, the output can be realized as necessary. For example, the pattern is formed by removing a portion of a metal foil used to form the heater by using wet etching, etc., or by printing the metal foil used to form the heater onto a ceramic sheet. In the case where wet etching or the like is used, the metal foil that remains without being removed is used to form the heater emitting heat due to an applied voltage. In other words, the electrostatic chuck includes a portion where the heater emitting heat is provided, and a portion where the heater is not provided.
Therefore, a temperature unevenness (an unevenness of the temperature) occurs in the electrostatic chuck according to the pattern of the heater. In other words, the temperature is high at the portion where the heater is provided; and the temperature is low at the portion where the heater is not provided. Even in the case of a wafer of which the temperature is controlled by the electrostatic chuck, a temperature unevenness occurs in the wafer surface due to the pattern of the heater; and the uniformity of the temperature distribution decreases.
In the case where two types of heaters are provided, the thickness of the entire heater increases; and there are cases where the response (the ramp rate) of the temperature of the wafer decreases. In other words, there are cases where the time necessary for controlling the temperature of the wafer undesirably lengthens.
The invention is based on a recognition of these problems and is directed to provide an electrostatic chuck in which the uniformity of the temperature distribution in the surface of the processing object can be increased.